A light emitting diode, which is a photoelectric conversion device having a structure in which an N-type semiconductor and a P-type semiconductor are joined together, emits light through recombination of electrons and holes. Such light emitting diodes have been widely used as display devices and backlights. Further, since the light emitting diode has less electric power consumption and a longer lifetime as compared with a conventional light bulb or fluorescent lamp, the light emitting diode is substituted for a conventional incandescent bulb or fluorescent lamp and has been widely used for the purpose of general illumination.
The light emitting diode is repeatedly turned on/off depending on the direction of a current under an AC power source. Thus, in a case where the light emitting diode is used while connected directly to the AC power source, there is a problem in that the light emitting diode does not continuously light and may easily be damaged by a reverse direction current.
To solve such a problem of the light emitting diode, a light emitting diode that can be used by connecting it directly to a high-voltage AC power source has been disclosed in PCT No. WO2004/023568(A1), entitled “LIGHT-EMITTING DEVICE HAVING LIGHT-EMITTING ELEMENTS” by SAKAI et al.
According to disclosed PCT No. WO2004/023568(A1), light emitting cells are two-dimensionally connected in series on an insulation substrate such as a sapphire substrate through metal wires to form LED arrays. Such two LED arrays are in reverse parallel on the substrate. As a result, the arrays are repeatedly turned on/off alternately by an AC power supply to emit light.
However, since the disclosed conventional technology is implemented through a unified method in which only one metal wire is always used with respect to one electrode when connecting electrodes of the adjacent light emitting cells through metal wires, various designs of AC light emitting diodes for enhancement of the intensity of light, prevention of flickering of light or the like have been limited.
As an example, if the conventional unified wire connection method is used in a case where the light emitting cells are arranged to constitute a matrix and an additional means for enhancing the intensity of light or the like is added as a portion of the elements of the matrix, there may be many difficulties in connecting the metal wires while avoiding the element added as the element of the matrix. Even though it is possible, there may be caused a problem in that the total length of the metal wires becomes extremely long.
Further, the disclosed conventional technology is configured such that the light emitting cells in the same line are repeatedly turned on/off at the same time, so that continuous and uniform light is not emitted from the substrate and thus flickering arises. In a case where the light emitting diode is used for a long time, such flickering may be a major cause for making human eyes fatigued although the flickering is not observed with naked eyes. The present inventors have conducted various studies for minimizing the aforementioned flickering, and found that the conventional unified wire connection method of using only one metal wire with respect to one electrode becomes a large obstacle in the implementation of a technique for minimizing the flickering.
An object of the present invention is to provide an AC light emitting diode wherein adaptable designs for enhancement of the intensity of light, prevention of flickering of light or the like become possible, while breaking from the conventional method of always using only one metal wire with respect to one electrode when electrodes of adjacent light emitting cells are connected through metal wires.
Another object of the present invention is to provide an AC light emitting diode wherein it is easier to employ a means such as a light guide portion for improvement of the intensity of light, while breaking from the conventional method of always using only one metal wire with respect to one electrode when electrodes of adjacent light emitting cells among light emitting cells arranged as elements of a matrix are connected through metal wires.
A further object of the present invention is to provide an AC light emitting diode wherein it is possible to solve disadvantages of the conventional technology, such as flickering of light, while breaking from the conventional method of always using only one metal wire with respect to one electrode when at least a pair of arrays are configured with light emitting cells arranged as elements of a matrix.
According to an aspect of the present invention, there is provided an AC light emitting diode comprising: a substrate; bonding pads positioned on the substrate; a plurality of light emitting cells arranged in a matrix form on the substrate; and a wiring means electrically connecting the bonding pads and the plurality of light emitting cells, wherein the wiring means at least includes a plurality of metal wires connecting an electrode of one of the light emitting cells with electrodes of other light emitting cells adjacent to the one of the light emitting cells.
Preferably, each of the plurality of light emitting cells has first and second electrodes of a P-type an N-type, a light emitting cell adjacent to two light emitting cells among the plurality of light emitting cells has a first electrode connected to a second electrode of one of the adjacent two light emitting cells through a metal wire, and a second electrode connected to a first electrode of the other of the adjacent two light emitting cells through another metal wire. Wherein, if first electrodes are P-type, then second electrodes are N-type. However, if first electrodes are N-type, then second electrodes are P-type.
Preferably, each of the plurality of light emitting cells has first and second electrodes of a P-type and an N-type, a light emitting cell adjacent to three light emitting cells among the plurality of light emitting cells has a first electrode connected to a second electrode of one of the adjacent three light emitting cells through a metal wire, and a second electrode connected to first electrodes of the others of the adjacent three light emitting cells through other two metal wires.
Preferably, each of the plurality of light emitting cells has first and second electrodes of a P-type and an N-type, a light emitting cell adjacent to four light emitting cells among the plurality of light emitting cells has a first electrode connected to first electrodes of two of the adjacent four light emitting cells through two metal wires, and a second electrode connected to second electrodes of the others of the adjacent four light emitting cells through other two metal wires.
Preferably, the AC light emitting diode according to the aspect of the present invention, further comprises light guide means further formed as an element of the matrix to focus light emitted from the plurality of light emitting cells adjacent to the at least light guide portion and to radiate the light to the outside. More preferably, the light guide means consists of a plurality of light guide portions regularly arranged at a predetermined interval.
According to another aspect of the present invention, there is provided an AC light emitting diode comprising: a substrate; bonding pads positioned on the substrate; a plurality of light emitting cells arranged as elements of a matrix on the substrate; and a wiring means electrically connecting the bonding pads and the plurality of light emitting cells, wherein the wiring means at least includes two metal wires connecting an electrode of one of the light emitting cells with electrodes of other light emitting cells adjacent to the one of the light emitting cells, and the plurality of light emitting cells include at least a pair of arrays of first and second arrays, and the two metal wires comprise a metal wire connecting the same kinds of electrodes of adjacent two of the light emitting cells provided in the same first or second array and a metal wire connecting first and second electrodes of adjacent two of the light emitting cells respectively provided in the first and second arrays.
According to the present invention, there is an advantage in that it is possible to design a variety of AC light emitting diodes for enhancing the intensity of light or minimizing flickering of light through a configuration of connecting one electrode of a light emitting cell as an element of a matrix to electrodes of other light emitting cells adjacent to the light emitting cell or to other matrix elements through two metal wires.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.